In oilfield operations, reciprocating pumps are used in fracturing subterranean formations in order to drill for oil or natural gas. A reciprocating pump typically includes a power end and a fluid end or cylindrical section. The fluid end is typically formed of a one piece construction or a series of blocks secured together by rods. The fluid end includes an opening for receiving a plunger or plunger throw, an inlet passage, an outlet passage, and an access port. A reciprocating pump, particularly in the oil-and-gas space, designed for fracturing operations is referred to as a “frac pump.” Such frac pumps can be seen, for example, in U.S. Pat. No. 9,822,894 issued on Nov. 21, 2017 to the assignee of the present application, which is incorporated herein by reference in its entirety for all purposes.
During operation of a frac pump, a fluid is pumped into the fluid end through the inlet passage and out of the pump through the outlet passage. The inlet and outlet passages each include a valve assembly, which is a check type of valve that is opened by differential pressure of the fluid and that allows the fluid to flow in only one direction. This fluid often contains solid particulates or corrosive material that can cause corrosion, erosion and/or pitting on surfaces of the valve assembly.
One particular area of erosion and pitting generally occurs on interacting surfaces of the valve assembly, which consists of a valve seat fixed into the inlet or outlet passages within the fluid end and a valve body that moves cyclically relative to the valve seat. In operation, the valve is operable between an open position, in which the valve body is spaced apart from the valve seat to facilitate fluid flow through the valve, and a closed position, in which the valve body contacts and sealingly engages the valve seat.
Conventional valve seat designs use a steel or other metal as both the valve and the valve seat, causing considerable friction and wear where the two meet as the valve engages the valve seat. Over time, repetitive contact of the metallic valve seat with the metallic valve causes specific portions of the valve or valve seat to wear out faster than other parts, leading to costly repair work to bring the frac pump back online. Because the valve seat is securely fastened within the fluid end, it is more difficult and cumbersome to replace the valve seat than the valve body. For example, a valve seat is oftentimes fixed inside the fluid passageway by way of an interference fit. Removing the valve seat from the fluid passageway oftentimes increases the risk of damage to the pump fluid end.